3:73 Gears in a 98 GT. difference in MPG & MPH?
 

my 98 has 3:73 gears in it and im wondering how off the spedo is at highway speeds (65 or so) and at city speeds (30-45).

also what differences do they make to MPG: City/ H.W.

It will increase your city mpg and lower you highway, but ultimately not changing mpg all that much. Im not sure about speedo, i would just get it calibrated so it doesnt rack up your miles and you dont get pulled over.

what do i need to get it calibrated?

Get either a speed calibrator or spend the penny for the tuner and get other benefits.

Here's my "How fast can I go in each gear?" calculator. Select your transmission (BW T-5) and 3.73 gears too see the chart for your car...

You dont have to spend all the money for the tuner or calibrator. Our years have mechanical speedos so you need to buy the correct one and just swap it out. And just so you know your gonna get like 300 posts saying go with 4.10s and dont fear the gear and every other corny line haha....

GO WITH 4.10s!!!!!!!!

Not gonna get you even close with just a mechanical speedo gear change
Gonna need a speed cal to correct as a tuner does not work on 98 back

or you can swap out your drive/speedo gear for much less then the cost of that. just saying, my 6 tooth drive gear and my 21 tooth speedo gears puts me almost dead even to my original set up, i think a little under 1 percent reading high... it will cost you about 15-20 dollars for the gears and the price of refilling your transmission.

http://allfordmustangs.com/forums/4-...haft-swap.html
here is a link that will help you out a bunch if you do this.


PS the 6/21 gear ratio is for the 4.10s, if you wanted it for 3.73's you need to get a different ratio

nothing that will put you close for 3.73's trust me